1. Field of the Invention
This invention relates generally to magnetic data storage devices, and more particularly to storage devices of the type commonly known as "Winchester" disk memories.
2. Description of the Prior Art
In the digital data storage devices known generically as "Winchester" disk memories, one or more rigid, rotatable magnetic disks and their associated magnetic head assemblies are sealed within a "clean chamber" in which air is continuously recirculated and filtered to exclude contaminants such as smoke and dust particles larger than about 0.3 micron. To prevent contamination during manufacture, final assembly of the drives and sealing of the clean chamber take place in a "clean room".
It is known that it is desirable to maintain the clean chamber at a positive pressure (see, for example, U.S. Pat. No. 3,740,735); in practice, however, this is not always achieved throughout the chamber. Where subatmospheric pressures exist--for example, in the areas about drive shafts that project through the clean chamber wall--points of potential leakage are created and contaminants, including particles dislodged from shaft bearings, can be drawn into the clean chamber. Often, this is particularly a problem in the vicinity of the disk drive motor spindle which, because of its location at the center of the rotating disk, is inherently at a low pressure point. The addition of impeller blades or vanes on the disk spindle for propelling the circulating air and assuring an adequate flow rate through the recirculating filter (which typically imposes a substantial pressure drop), often aggravates the problem by further decreasing the pressure in the vicinity of the spindle.
Another potential source of contamination in prior art Winchester drives is the head assembly positioning mechanism. These positioners may take various forms including, for example, split-band drives of the type disclosed in U.S. Pat. Nos. 4,161,004 and 4,164,769 or linear positioners using bearings and ways, for example, U.S. Pat. No. 3,665,433. Many of the elements of these positioners, including the band and the drive capstan about which the band is wrapped, and/or the bearings and ways, are enclosed within the clean chamber. At the band/capstan and bearing/way interfaces, small amplitude, repetitive motion occurs. This relatively high frequency motion with concomittant small amplitude slippage, causes a type of wear known as fretting wear or fretting corrosion. Also, all bearings in the system contain lubricants with volatile components. As a result, because of corrosion, wear, evaporation and so forth, those elements may produce a variety of contaminants that are entrained or swept up by the air flow and transported to the head/disk area.